Methods and Apparatuses for Dynamic Transmit Diversity Fallback

1. An apparatus, comprising: at least one processor; and at least one memory comprising computer program code, the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to configure a user equipment with a maximum number of multiple-input multiple-output layers used for transmission mode 9 or transmission mode 10 scheduling; perform at least one of transmission mode 9 or transmission mode 10 scheduling, wherein the configuring comprises indicating to the user equipment to use a modified mapping table providing transmit diversity fallback with shorter transmission time interval physical downlink shared channel for the at least one of transmission mode 9 or transmission mode 10 scheduling.

2. The apparatus according to claim 1 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is 2, the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to indicate to the user equipment to use at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 2 layers.

3. The apparatus according to claim 2 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least entries in the non-modified table for 3-layer and 4-layer transmission with 2-layer transmission diversity fallback entries.

4. The apparatus according to claim 1 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is greater than 2, the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to indicate to the user equipment to use at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 4 layers.

5. The apparatus according to claim 4 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least one entry in the non-modified table for 2-layer spatial multiplexing transmission with a 2-layer transmission diversity fallback entry.

6. The apparatus according to claim 1 , wherein the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to receive a report from the user equipment of the maximum number of multiple-input multiple-output layers supported for physical downlink shared channel.

7. The apparatus according to claim 1 , wherein the configuration comprises a dedicated configuration of maximum multiple-input multiple-output layers, or wherein the configuring depends on number of channel station information reference signal ports, or the configuring is performed through codebook subset restriction.

8. A method, comprising: receiving, from a network node, a configuration of a maximum number of multiple-input multiple-output layers used for transmission mode 9 or transmission mode 10 scheduling; using, based on the received configuration, a modified mapping table providing transmit diversity fallback with shorter transmission time interval for at least one of transmission mode 9 or transmission mode 10 downlink shared channel reception.

9. The method according to claim 8 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is 2, the using further comprises using at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 2 layers.

10. The method according to claim 9 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least the entries in the non-modified mapping table for 3-layer and 4-layer transmission with 2-layer transmission diversity fallback entries.

11. The method according to claim 8 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is greater than 2, the using further comprises using at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 4 layers.

12. The method according to claim 11 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least the entries in the non-modified table for 3-layer and 4-layer transmission with 2-layer transmission diversity fallback entries.

13. The method according to claim 8 , further comprising reporting, to a network node, a maximum number of downlink shared channel multiple-input multiple-output layers that are supported.

14. A non-transitory computer readable medium comprising program instructions stored thereon for performing at least the method according to claim 8 .

15. An apparatus, comprising: at least one processor; and at least one memory comprising computer program code, the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to receive, from a network node, a configuration of a maximum number of multiple-input multiple-output layers used for transmission mode 9 or transmission mode 10 scheduling; use, based on the received configuration, a modified mapping table providing transmit diversity fallback with shorter transmission time interval for at least one of transmission mode 9 or transmission mode 10 downlink shared channel reception.

16. The apparatus according to claim 15 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is 2, the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to use at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 2 layers.

17. The apparatus according to claim 16 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least the entries in the non-modified mapping table for 3-layer and 4-layer transmission with 2-layer transmission diversity fallback entries.

18. The apparatus according to claim 15 , wherein, when a maximum number of multiple-input multiple-output layers supported for physical downlink shared channel is greater than 2, the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to use at least one modified mapping table providing transmit diversity fallback for the at least one of transmission mode 9 or transmission mode 10 scheduling for up to 4 layers.

19. The apparatus according to claim 18 , wherein the at least one modified mapping table differs from a non-modified table by replacing at least the entries in the non-modified table for 3-layer and 4-layer transmission with 2-layer transmission diversity fallback entries.

20. The apparatus according to claim 15 , wherein the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to report, to a network node, a maximum number of downlink shared channel multiple-input multiple-output layers that are supported.